/*
 * Copyright 2021 Shulie Technology, Co.Ltd
 * Email: shulie@shulie.io
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.shulie.surge.data.runtime.disruptor;

/**
 * Yielding strategy that uses a Thread.yield() for {@link com.lmax.disruptor.EventProcessor}s waiting on a barrier
 * after an initially spinning.
 *
 * This strategy is a good compromise between performance and CPU resource without incurring significant latency spikes.
 */
public final class YieldingWaitStrategy implements WaitStrategy
{
	private static final int SPIN_TRIES = 100;

	@Override
	public long waitFor(final long sequence, Sequence cursor, final Sequence dependentSequence,
			final SequenceBarrier barrier)
			throws AlertException, InterruptedException
	{
		long availableSequence;
		int counter = SPIN_TRIES;

		while ((availableSequence = dependentSequence.get()) < sequence)
		{
			counter = applyWaitMethod(barrier, counter);
		}

		return availableSequence;
	}

	@Override
	public void signalAllWhenBlocking()
	{
	}

	private int applyWaitMethod(final SequenceBarrier barrier, int counter)
			throws AlertException
	{
		barrier.checkAlert();

		if (0 == counter)
		{
			Thread.yield();
		}
		else
		{
			--counter;
		}

		return counter;
	}
}
